1. Field of the Invention
The invention relates to a zoom lens device, more particularly to a zoom lens device having a relatively wide zoom adjusting range.
2. Description of the Related Art
Referring to FIGS. 1, 2 and 3, a conventional zoom lens device is capable of zooming along an axis (A). The zoom lens device includes a base barrel 1, a rotating barrel 2 surrounding and rotatable relative to the base barrel 1, a cam barrel 3 connected to the base barrel 1, co-rotatable with the rotating barrel 2, and movable relative to the base barrel 1 along the axis (A), first and second guide barrels 4, 5 connected co-movably to the cam barrel 3 along the axis (A), a first lens barrel 6 connected to the first guide barrel 4 and movable relative to the first guide barrel 4 along the axis (A), a second lens barrel 7 connected to the second guide barrel 5 and movable relative to the second guide barrel 5 along the axis (A), and a plurality of guide pins (not shown). The base barrel 1 is formed with a plurality of angularly spaced-apart guide grooves 101. Each guide pin is secured fixedly to the cam barrel 3, extends slidably through a respective one of the guide grooves 101, and is connected slidably to the rotating barrel 2. The cam barrel 3 has an outer surrounding surface formed with a plurality of angularly spaced-apart first cam grooves 301, and an inner surrounding surface formed with a plurality of angularly spaced-apart second cam grooves 302. The first lens barrel 6 has a plurality of angularly spaced-apart first pins 601 engaging slidably and respectively the first cam grooves 301. The second lens barrel 7 has a plurality of angularly spaced-apart second pins 701 engaging slidably and respectively the second cam grooves 302. The rotating barrel 2 is rotatable to drive rotation of the cam barrel 3 and therefore to cause axial movements of the first and second lens barrels 6, 7 via the engagement between the guide pins and the guide grooves 101, the engagement between the first pins 601 and the first cam grooves 301, and the engagement between the second pins 701 and the second cam grooves 302.
When the rotating barrel 2 is driven to rotate by a motor (not shown), the conventional zoom lens device can switch between a telephoto state (see FIG. 2) where the first and second lens barrels 6, 7 are close to each other, and a wide-angle state (see FIG. 3) where the first and second lens barrels 6, 7 are far from each other.
The axial movement of the first lens barrel 6 relative to the base barrel 1 is guided cooperatively by the guide grooves 101 and the first cam grooves 301, and the axial movement of the second lens barrel 7 relative to the base barrel 1 is guided cooperatively by the guide grooves 101 and the second cam grooves 302 in the cam barrel 3. Although the first lens barrel 6 of this conventional zoom lens device has a long extent in stretching relative to the base barrel 1, when the first lens barrel 6 and the cam barrel 3 are at their utmost stretching positions, the axial movement of the second lens barrel 7 along the axis (A) relative to the first lens barrel 6 is limited by a thickness and the position of the cam barrel 3. As a result, the conventional zoom lens device has relatively small zoom adjusting range.
Taiwanese Patent Application Publication No. 201013247 discloses another conventional zoom lens device which includes two lens barrels connected to an inner surface of a cam barrel of the zoom lens device. As such, only a single guide barrel is required to guide linear motions of the two lens barrels. However, such zoom lens device with fewer elements also has the abovementioned drawback.